ANTITHYROID ACTIVITY ELICITED BY THE INGESTION OF PURE PROGOITRIN, A NATURALLY OCCURRING THIOGLYCOSIDE OF THE TURNIP FAMILY*

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Abstract
Previous studies have shown that certain foods, especially rutabaga and turnip, possess antithyroid activity in man. The active antithyroid principle of the turnip family, goitrin, is released from a precursor, progoitrin, by enzymatic action. Earlier studies had indicated that cooking foods containing progoitrin would destroy myrosin, the specific hydrolytic enzyme which liberates goitrin from progoitrin. It was suggested that the cooked foods would have no antithyroid activity when eaten. Studies were made with crystalline progoitrin in man and the laboratory rat employing inhibition of radioiodine uptake as an index of antithyroid activity. Contrary to expectations, it was found that progoitrin would produce consistent antithyroid activity either with or without simultaneous administration of myrosin. It was possible to identify the appearance of goitrin in the blood and urine by spectrophotometric analysis and to determine that the yield of goitrin from progoitrin was quantitative. This indicated that hydrolysis of progoitrin occurs within the body in the absence of exogenous myrosin. This demonstration of antithyroid activity following the administration of pure progoitrin suggests that our concept regarding the innocuousness of cooked crucifers in the production of simple goiter should be revised. Progoitrin administered in a single daily dose of one g was found to be an effective agent in the treatment of thyrotoxicosis in one patient.